With LVM, Why Use RAID?

Given that LVM has some features similar to RAID (the ability to dynamically replace failing drives, for instance), and some features providing capabilities that cannot be matched by most RAID implementations (such as the ability to dynamically add more storage to a central storage pool), many people wonder whether RAID is no longer important.
Nothing could be further from the truth. RAID and LVM are complementary technologies that can be used together (in a manner similar to nested RAID levels), making it possible to get the best of both worlds.